Airflow management for low particulate count in a process tool

ABSTRACT

A method of providing airflow management in a substrate production tool includes providing a first mechanism coupling the substrate production tool to a fan filter unit. The fan filter unit provides filtered air to the substrate production tool. A second mechanism couples the substrate production tool to a reduced pressure exhaust mechanism. The reduced pressure exhaust mechanism provides an exhaust for excess gas flow within the substrate production tool. A substrate process area of the substrate production tool is maintained at a lower pressure than a pressure of a substrate transfer section of the substrate production tool. The substrate process area maintains a higher pressure than a pressure of the reduced pressure exhaust mechanism. The substrate transfer section maintains a higher pressure than the pressure of the reduced pressure exhaust mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is a divisional of U.S. patent application Ser.No. 12/730,868 filed on Mar. 24, 2010. The entire disclosures of theapplications referenced above are incorporated herein by reference.

TECHNICAL FIELD

The present application relates generally to the field of semiconductorprocessing and, in a specific exemplary embodiment, to a system andmethod of controlling particulate count within a processing chamber.

BACKGROUND

In the manufacture of semiconductor devices, process chambers arefrequently interfaced to permit transfer of wafers or substrates, forexample, between the interfaced chambers. The transfer is typicallyperformed via transfer modules that move the wafers, for example,through slots or ports that are provided in adjacent walls of theinterfaced chambers. Transfer modules are generally used in conjunctionwith a variety of wafer processing modules (PMs), which may includesemiconductor etching systems, material deposition systems, and flatpanel display etching systems.

Semiconductor device geometries (i.e., integrated circuit design rules)have decreased dramatically in size since such devices were firstintroduced several decades ago. Integrated circuits (ICs) formed in theprocess chambers have generally followed “Moore's Law,” meaning that thenumber of devices that fit onto a single integrated circuit chip doublesevery two years. Contemporary IC fabrication facilities (“fabs”)routinely produce 65 nm (0.065 μm) feature size devices and smaller.Future fabs will soon be producing devices having even smaller featuresizes. Commensurate with the reduced feature sizes are reducedcontamination and particle budgets as even a single 30 nm particle canbe a killer defect for a given IC.

Perhaps more importantly, from a yield and cost basis standpoint, thetypes of equipment (e.g., process tools) used in the fabrication processis becoming a primary technology driver. The fabrication process must beeffective, but it must also be fast and not add to the total particle orcontamination budget. Contemporary throughput demands for currentgenerations of 300 mm wafers in many applications are 360 wafers perhour or higher. Currently, systems use only a single carrier linearwafer motion requiring a non-productive time period while the wafercarrier is returned to a starting point in a process tool. Thus, waferhandling is slow. Proposed solutions to increase throughput have focusedon joining a plurality of process tools in parallel. While suchsolutions may increase wafer throughput, they do so at the expense oftool footprint, increased equipment costs, reduced reliability, and, inmany cases, increased particle generation from wafer transportmechanisms within the tools. Accordingly, improvements are needed in thefield of semiconductor processing with a special emphasis on equipmentreliability, throughput, and efficiency.

BRIEF DESCRIPTION OF DRAWINGS

Various ones of the appended drawings merely illustrate exemplaryembodiments of the present invention and cannot be considered aslimiting its scope.

FIG. 1A is an exploded perspective view of an exemplary substrateprocessing tool, including an equipment front-end module (EFEM), aprocess module, and an electronics enclosure, incorporating at leastaspects of the inventive subject matter described herein;

FIG. 1B is a perspective view of the process module of FIG. 1A includinga process chamber;

FIG. 2 is a perspective view of an exemplary clock-arm substrate carriermechanism used within the process chamber of FIG. 1B;

FIG. 3 is a perspective view of an exemplary substrate traversermechanism to be used in conjunction with the clock-arm substrate carriermechanism of FIG. 2 and within the process chamber of FIG. 1B;

FIG. 4 is a plan view of the clock-arm substrate carrier mechanism ofFIG. 2 used in conjunction with the substrate traverser mechanism ofFIG. 3 in an exemplary embodiment;

FIG. 5A is a perspective view of a lower portion of the process chambershowing exemplary process chamber exhaust and drain locations used withthe exemplary clock-arm substrate carrier mechanism and the substratetraverser mechanism of FIG. 4 and located within the process module ofFIG. 1B;

FIG. 5B is a perspective view showing an exemplary process chamberexhaust and drain system used within the process module of FIG. 1B;

FIG. 6 is an exemplary air handling schematic showing volumetric flowrates into and out from the EFEM and the process module of FIG. 1A;

FIG. 7A is an exemplary perspective view and an exemplary plan view ofsolid components of the process chamber of FIG. 1B used in computationalfluid dynamic (CFD) modeling;

FIG. 7B is a perspective view and a side elevational view (both views onone side of a line of symmetry) of a fluid domain of the process chamberof FIG. 1B used in the computational fluid dynamic modeling utilizingthe solid components of FIG. 7A;

FIG. 7C is a computed particle trace for a perspective view, a planview, and a side elevational view (all three views on one side of a lineof symmetry) of general air flow motion within the process chamber ofFIG. 1B;

FIG. 7D is a computed pressure field for a perspective view and a planview (both views on one side of a line of symmetry) to verify locationsof negative pressure within the process chamber of FIG. 1B;

FIG. 7E is a computed velocity flow field for a perspective view (on oneside of a line of symmetry) of general air flow motion from ahigh-efficiency particulate air filter (HEPA) inlet within the processchamber of FIG. 1B;

FIG. 7F is a computed velocity flow field for a perspective view (on oneside of a line of symmetry) of general air flow motion from a hood slitin the chamber inlet within the process chamber of FIG. 1B to outletlocations as indicated by FIGS. 5A and 5B;

FIG. 7G is a computed velocity flow field for a side elevational view(on one side of a line of symmetry) of general air flow motion from theHEPA inlet and the hood slit around a chamber ionizer bar within theprocess chamber of FIG. 1B; and

FIG. 7H is a computed pressure field for a side elevational view (on oneside of a line of symmetry) of pressure gradients from the HEPA inletand the hood slit within the process chamber of FIG. 1B.

DETAILED DESCRIPTION

The description that follows includes illustrative systems, methods, andtechniques that embody various aspects of the inventive subject matterdiscussed herein. In the following description, for purposes ofexplanation, numerous specific details are set forth to provide anunderstanding of various embodiments of the inventive subject matter. Itwill be evident, however, to those skilled in the art that embodimentsof the inventive subject matter may be practiced without these specificdetails. Further, well-known operations, structures, and techniques havenot been shown in detail.

As used herein, the term “or” may be construed in either an inclusive oran exclusive sense. Similarly, the term “exemplary” is construed merelyto mean an example of something or an exemplar and not necessarily apreferred or ideal means of accomplishing a goal. Additionally, althoughvarious exemplary embodiments discussed below focus on substratetransport mechanisms and related contamination-related reductiontechniques, the embodiments are given merely for clarity in disclosure.Thus, any type of substrate transport mechanism can employ variousembodiments of the system described herein and is considered as beingwithin a scope of the present inventive subject matter.

Moreover, as used herein, the term “substrate” is simply chosen as aconvenient term referring to any of various substrate types used in thesemiconductor and allied industries. Substrate types may thereforeinclude silicon wafers, compound wafers, thin film head assemblies,polyethylene-terephthalate (PET) films, photomask blanks and reticles,or numerous other types of substrates known in the art.

In various exemplary embodiments described in detail herein, a methodand system to provide filtered air is disclosed that reduces particulatecontamination from contact with substrates being transported orprocessed in a process tool such as, for example, a wafer-cleaning toolused in the semiconductor industry. The method and system furthermaintain chemical and vapor containment in a substrate pass-throughdesign while allowing for demand variations of the chemical area of aprocess chamber within the tool. A filtering unit provides air fromabove the substrates. The filtering unit can be moved for maintenanceand has a gap above the substrate transport and processing area makingthe unit easy to move while reducing vibration transfer. In an exemplaryembodiment, air enters the chemical section of the process chamberthrough a slot designed to provide a pressure difference between thechemical section and a substrate transfer section. Substrates exit thechemical zone through slots that minimize airflow from a lower region ofthe chamber. The dominant airflow into the chemical region is through anupper slot that reduces particles from being swept up from lowersurfaces of the chamber. Where the substrate transport mechanism passesthrough to the chemical area of the chamber, the substrates pass throughtwo slits in which a pressure differential is maintained thus pullingparticles away from the chemical area while keeping chemical vapors fromthe non-chemical area. Various ones of the exemplary embodimentsdescribed herein thus allow for air velocities on surfaces of thesubstrates to be low while the substrates go through the slitsseparating the various regions within the chamber. Various ones of theexemplary embodiments further reduce or prevent chemical vapors fromleaving chemical regions, and provide for sweeping of air from highparticle regions reaching the substrates.

In another exemplary embodiment, airflow created by a designed pressuredifferential reduces or prevents particles from migrating from multiplelinear substrate transporters having exposed linear belts. As describedherein, multiple substrate carriers driven by linear belt drive slidestend to be particle generators due to friction and moving mechanicalparts. Particles generated from the slides or belts are ideallyprevented from getting on the substrates. Using governing equations forparticle terminal velocities, airflow requirements were determinedacross a horizontal slot that substrates traverse to connect them to thelinear slides. A required airflow velocity was determined for particlessizes less than about 50 μm to flow faster than a terminal velocity ofthe particle size ranges of interest. Particles larger than 50 μm wouldfall at high enough rates that they could not traverse the horizontalslot. Baffling was designed to make the slot flow uniform even with thedraw for the slit being at one end.

Thus, in an exemplary embodiment, a system to provide airflow managementin a substrate production tool is disclosed. The system includes ahousing to couple the substrate production tool to a fan filter unit toprovide filtered air to the housing, a facility connection to couple thesubstrate production tool to a reduced pressure exhaust mechanism, asubstrate transfer section coupled below the housing and in airflowcommunication with the facility connection, and a substrate process areacoupled to the substrate transfer section by one or more substratetransfer slots. A chamber substantially containing the substratetransfer section and the substrate process area is coupled to thehousing to receive the filtered air and to the facility connection toprovide an exhaust for excess gas flow. The chamber maintains a lowpressure in the substrate process area relative to the substratetransfer section.

In another exemplary embodiment, a system to provide airflow managementin a wafer process tool is disclosed. The system includes a fan filterunit to provide filtered air to the wafer process tool, a facilityconnection to couple the wafer process tool to a reduced pressureexhaust mechanism of a wafer fabrication facility, a wafer transfersection coupled below the fan filter unit and in airflow communicationwith the facility connection, and a wafer process area having a chemicalprocess section. The wafer process area is coupled to the wafer transfersection by one or more wafer transport slots. A process chambersubstantially containing the wafer transfer section and the waferprocess area is coupled to the fan filter unit to receive the filteredair and to the facility connection to provide an exhaust for excess gasflow. The process chamber maintains a low pressure in the wafer processarea relative to the wafer transfer section.

In another exemplary embodiment, a method of providing airflowmanagement system in a substrate production tool is disclosed. Themethod includes providing a first mechanism to couple the substrateproduction tool to a fan filter unit to provide filtered air to thesubstrate production tool and providing a second mechanism to couple thesubstrate production tool to a reduced pressure exhaust mechanism toprovide an exhaust for excess gas flow within the substrate productiontool. A substrate process area of the substrate production tool ismaintained at a lower pressure than a pressure of the substrate transfersection of the substrate production tool while the substrate processarea is maintained at a higher pressure than a pressure of the reducedpressure exhaust mechanism. The substrate transfer section is maintainedat a higher pressure than the pressure of the reduced pressure exhaustmechanism.

With reference to FIG. 1A, an exploded perspective view of pieces ofequipment used to process substrates, such as semiconductor wafers, isshown. A processing tool 100 (commonly referred to as a process tool orother substrate production tool) is shown to include an equipmentfront-end module (EFEM) 110, a process module 130, and an electronicsenclosure 150.

In operation, the EFEM 110, the process module 130, and the electronicsenclosure 150 are unified as a single unit. The process module 130includes a process chamber 131 (or other chamber types in whichsubstrates are located, such as, for example, an in-situ metrologychamber). The process chamber may include a substrate transfer sectionand a substrate process area, both defined in detail, below, in whichvarious processes are performed on a batch of substrates. The processesmay include various types of, for example, substrate cleaning andwet-etch (e.g., chemical etch) steps known independently in thesemiconductor and related art fields. Additionally, the process module130 is generally enclosed to reduce any particulate, organic, or othercontamination of substrates within the process module 130 and theprocess chamber 131. Further, the enclosure (not shown) minimizes a riskof hazardous interactions between an equipment operator and movingmechanisms within the process module 130, thereby increasing safety ofthe operator. Operating power is supplied to the EFEM 110 and theprocess module 130 by the electronics enclosure 150.

The EFEM 110 is shown to include a number of substrate load stations111, a first operator control interface 115A, and a second operatorcontrol interface 115B. From one of these control interfaces, anoperator may input and run, for example, process recipes for aparticular batch of substrates. The EFEM 110 is also shown to include afront opening unified pod (FOUP) 113 placed on one of the substrate loadstations 111. The FOUP 113 is a particular type of plastic enclosuredesigned to hold semiconductor wafers (e.g., generally silicon wafers(Si) but may also include various other wafer types formed fromelemental semiconductor materials such as germanium (Ge), or compoundsemiconductor materials such as gallium-arsenide (GaAs) or indiumarsenide (InAs)). The FOUP 113 holds the wafers (not shown) securely andsafely in a controlled environment. Although not shown explicitly inFIG. 1A, a skilled artisan will recognize readily that a FOUP maysimultaneously be present on each of the substrate load stations 111.One or more robots (not shown) may be associated with each FOUP.

Once the FOUP 113 is placed on one of the substrate load stations 111,the robot (not shown) within the EFEM 110 may directly access the waferscontained within the FOUP 113. The EFEM 110 thus allows an operator toload and unload substrates from the FOUP 113 into the process chamber131 via, for example, a two-bladed or four-blade robot (not shown butknown independently in the art). Although not limited to a particularrobot type, one robot that can be employed is, for example, a modelFC06N, manufactured by Kawasaki (USA), Inc. of Wixom, Mich., USA. In aspecific exemplary embodiment, the robot may incorporate a collapsiveend-effector having four 3.8 mm blades with an approximate 10 mm spacingbetween adjacent blades. The 10 mm spacing is matched to thewafer-to-wafer spacing in a typical FOUP. Details of various transportprocesses occurring within the process chamber 131 are described in moredetail with reference to FIGS. 4, 5B, and 5B, below.

Referring now to FIG. 1B and with concurrent reference to FIG. 1A,substrates (not shown) are transported by the robots from the FOUP 113to one of a number of substrate carriers 135 (i.e., rotary-mountedsubstrate carriers) located on a clock-arm substrate carrier mechanism(not shown explicitly in either FIG. 1A or FIG. 1B but described indetail with reference to FIG. 2, below). The substrate is loaded orunloaded into or out of the process chamber 131 through a substratetransport slot 133.

A high-efficiency particulate air (HEPA) filter placed within a fanfilter unit (FFU) 137 provides substantially clean air within theprocess chamber 131. The FFU 137 is located above the process chamber131 to provide airflow and particular pressure gradients within thechamber to reduce particulate contamination on and around substrates.The airflow partially reduces particulate contamination by a producing aboundary layer above the substrate through which small particles areunable to pass. Both large and small particles are then swept out of theprocess chamber 131 and into an exhaust system, described below.Improved chemical containment is also achieved through use of theproduced pressure gradients (described in more detail, below).

Although the FFU 137 is described as employing a HEPA filter herein, askilled artisan will recognize that other filter types (e.g., anultra-low particulate air (ULPA) filter) could readily be substitutedfor the HEPA filter with added fan capacity as needed to account for ahigher pressure-drop across, for example, the ULPA filter. Calculationof the airflow and pressure gradients produced by the FFU 137 isdiscussed with reference to FIGS. 6-7H, below. The process chamber 131is also shown to include ionizer bars 139 that run parallel to a longaxis of the FFU 137. The ionizer bars 139 reduce electrostatic chargesthat would otherwise accumulate on substrates within the process chamber131 caused by friction generated by the airflow across the substratesfrom the FFU 137. A substrate with a charge more readily attractsoppositely charged particles. As is known to a skilled artisan, theability of an ionizer to reduce charge on any surface (e.g., thesubstrate) is time dependent. Therefore, the ionizer bars 139 can belocated relative to the substrates (located beneath the ionizer bars)where a relatively long residence time (e.g., 1 second to 5 seconds butat least partially dependent on localized airflow) assists in producingan intended reduction in electrostatic charge on the substrates. Theionizer bars 139 can be located in other positions within the processchamber 131, may be unipolar (i.e., producing anions or cations) orbipolar (i.e., a balanced ion generator), may be of other sizes andshapes, and may be instantiated in numerous positions within the processchamber 131 above the substrates. In a specific exemplary embodiment,the ionizer bars 139 are approximately 64 inches (about 1.63 m) inlength.

In a specific exemplary embodiment, the FFU 137 has a volumetric flowrate of approximately 910 cubic feet per minute (cfm, or about 25.8 m³per minute) with a face velocity from an outlet side of the HEPA filterbeing approximately 90 feet per minute (fpm, or about 27.4 m perminute). In other embodiments, the FFU 137 has a volumetric flow rate ofapproximately 1300 cubic feet per minute (about 36.8 m³ per minute). TheHEPA filter can be formed from a tetrafluoroethylene (TFE) material witha 99.99995% filter efficiency at 0.3 μm. A skilled artisan willrecognize that the ULPA filter, described above, can have an even higherefficiency (as measured at 0.12 μm). The FFU 137 and the process chamber131 are designed so that less than five particles at a size of 55 nm andlower are added due to substrate transport considerations.

With continued reference to FIG. 1B, a first chamber exhaust pipe 141and a second chamber exhaust pipe 143 draw particulates and fluids(e.g., excess process gases, such as air produced by the FFU 137, andexcess process liquids) from opposite sides of the process chamber 131into a cross-tube assembly 145. In an exemplary embodiment, a chamberexhaust stack 147 provides makeup airflow allowing particulates andfluids entering the cross-tube assembly 145 to be readily drawn into anexhaust/drain system (not shown) within the fabrication facility. Inother exemplary embodiments, the chamber exhaust stack 147 mayoptionally be coupled to an exhaust connection within the fabricationfacility to provide an air draw. More detail on the exhaust system isgiven, below, with reference to FIGS. 5A and 5B.

FIG. 2 shows an exemplary embodiment of a clock-arm substrate carriermechanism 200. The clock-arm substrate carrier mechanism 200 is shown toinclude a number of rotary arms 201, with each end of the rotary arms201 having an associated one of the substrate carriers 135, an innertrack section 203, an outer track section 205, and substrate lifters207. Each of the rotary arms 201 may be driven independently and, thus,may be started, stopped, and accelerated independently of the remainingones of the rotary arms 201. Additionally, although only four of therotary arms 201 are shown, the clock-arm substrate carrier mechanism 200can be adapted to handle any number of arms. The number of arms will beat least partially dependent upon a physical size of, for example, adiameter of the outer track section 205 and a physical size of each thesubstrate carriers 135. The rotary arms 201 and the substrate carriers135 may be scaled as necessary to adapt to a given substrate size. Forexample, the substrate carriers 135 may be designed to accommodate 300mm silicon wafers, 100 mm gallium arsenide (GaAs) wafers, or a nextgeneration of 450 mm wafers.

In a specific exemplary embodiment, the outer track section 205 isphysically arranged to accommodate a 30 inch (approximately 760 mm)radius from midpoints of the rotary arms 201 to a center of thesubstrate carriers 135. As discussed, above, the outer track section 205can be sized appropriately depending upon the number of rotary armsemployed and the size of the substrates handled.

The substrate lifters 207 may be of any general type commonly known andused in, for example, the semiconductor industry. As shown, twoinstantiations of the substrate lifters 207 are spaced approximately180° apart from one another. In other embodiments (not shown), there maya higher number of substrate lifters 207 used.

Additionally, one or both of the substrate lifters 207 may be rotated180° to correct for the 180° rotation of a substrate through theclock-arm substrate carrier mechanism 200. The rotation occurs wouldthus occur between when moving a substrate between the clock arm carrierand the linear carrier as discussed, below. When only one of thesubstrate lifters 207 is rotating 180°, the 180° rotation occurs on themoving of a substrate from the clock carrier into the linear carrier andon the moving a substrate from the linear carrier to the clock carrier.

In general operation, once a particular one of the substrate carriers135 is positioned over one of the substrate lifters 207, an externalrobot (not shown) may place a wafer to or from a substrate carrier(e.g., a wafer boat or the FOUP 113) onto one of the substrate lifters207. The selected one of the substrate lifters 207 then lowers thesubstrate onto to the particular one of the substrate carriers 135 andthe lifter continues to lower itself far enough to avoid any collisionswith any of the rotary arms 201 or any other moving mechanisms containedwithin the clock-arm substrate carrier mechanism 200.

With continued reference to FIG. 2, the clock-arm substrate carriermechanism 200 further includes an upper chemical-release head 211 and alower chemical-release head 213 situated so as to spray or otherwiseapply chemicals (e.g., such as various combinations of the cleaning oretching chemicals) as a substrate passes in proximity to the upperchemical-release head 211 and a lower chemical-release head 213.Utilizing at least two heads allows chemicals to be applied to bothsides of a wafer in a single pass without a need to invert thesubstrate. Alternatively, the upper chemical-release head 211 and alower chemical-release head 213 may be arranged to apply chemicals toboth sides of a substrate simultaneously. As will be recognizable to askilled artisan, any number of chemical-release heads may be utilized.

In a specific exemplary embodiment, the upper chemical-release head 211and a lower chemical-release head 213 are each designed in a“pie-section” shape, having a wider cross-sectional width at an outerperiphery of the clock-arm substrate carrier mechanism 200 than at aninner periphery. The pie-section shape accommodates a higher angularvelocity on the outermost portion of the substrate as compared with theinner portion. Thus, more chemicals may be delivered to an outer portionof the substrate through, for example, an increased number of spraynozzles directed at the substrate, thus insuring uniform chemicalcoverage over each face of the substrate.

As a result of various features described herein, the clock-armsubstrate carrier mechanism 200 can provide for continuous flowmanufacturing and lends itself to processing without significanttemporal gaps between successive substrates. As noted above, wetchemical cleaning or etching can involve a number of various steps.Starting and stopping wet chemistry is hard to control, wasteful, andinefficient. The clock-arm substrate carrier mechanism 200 processessubstrates in a continuous mode by having each of the substrate carriers135 travel in a full 360° arc. Unlike various prior art systems thatprovide only linear systems requiring a 180° return in which no wafercleaning or processing occurs, the clock-arm substrate carrier mechanism200 may run parallel cleaning processes on opposing sidessimultaneously. Consequently, chemical control can be shared, therebyreducing control system overhead and redundant circuitry. As such,chemical savings can be as much as 300% (i.e., a four-time reduction inchemical usage) from contemporary linear systems.

Within the process chamber 131 (see FIG. 1B), at least two parallelprocesses occur simultaneously: chemical control and substrate motion.As described in more detail with reference to FIG. 3, below, independentcontrol of velocities and accelerations of the substrate carriers 135allows for an exit step and for loading and unloading one or moresubstrates substantially simultaneously. The independent control of thesubstrate carriers 135 further allows a carrier to accelerate to catchup in a process flow once a carrier has been loaded or unloaded, alsodescribed in more detail, below.

With reference now to FIG. 3, an exemplary embodiment of a substratetraverser mechanism 300 is shown to include a pair of upper tracks 301,a pair of lower tracks 303, a pair of right-mounted substrate carriers305, and a pair of left-mounted substrate carriers 307. The substratecarriers, as shown, are movable in different planes that are parallel toone another as well as being in planes parallel to the rotary arms 201of the clock-arm substrate carrier mechanism 200. Each of the carriersis also shown as holding a semiconductor substrate 311 merely to assistin describing the overall movement and transport of substrates, below.An indication of where the substrate traverser mechanism 300 is locatedin reference to the substrate transport slot 133 is also shown in FIG.3.

Each of the pair of right-mounted substrate carriers 305 and the pair ofleft-mounted substrate carriers 307 is driven in a linear mannerindependently by a motor 309. The motor can be selected from a number ofmotor types. For example, in a specific exemplary embodiment, each ofthe motors 309 may be a standard NEMA 23 frame dimensions such as anSM2315D servo motor with an integral encoder (available from AnimaticsCorporation, 3200 Patrick Henry Drive, Santa Clara, Calif., USA).Although not shown explicitly, the carriers are driven by the motor 309associated with a given carrier by a linear actuator (e.g., a linearbelt drive system). Such linear actuator systems are known independentlyin the art. For example, a Festo® EGC-50 belt driven linear actuator(manufactured by FESTO KG, Ruiter Strasse 82, Esslingen, FederalRepublic of Germany) may be employed as a carrier drive mechanism forthe substrate traverser mechanism 300.

As described herein in various exemplary embodiments, the substratetraverser mechanism 300 is shown to have only a particular number oftracks, substrate carriers, motors, and associated drive mechanisms.However, a skilled artisan will recognize that the concepts describedherein may readily be extrapolated to any number or tracks and substratecarriers.

Referring now to FIG. 4, an exemplary embodiment shows a plan view 400of the clock-arm substrate carrier mechanism 200 (see FIG. 2) inconjunction with the substrate traverser mechanism 300 (see FIG. 3). Inthis exemplary embodiment, the substrate traverser mechanism 300operates above the clock-arm substrate carrier mechanism 200.

An exemplary operation of the combined clock-arm and traverser mechanismis now described with concurrent reference to FIGS. 2 and 4. After asubstrate has been processed in the process chamber 131 (see FIG. 1B),one of the rotary arms 201 is temporarily stopped above one of thesubstrate lifters 207 (e.g., the lifter located opposite the substratetransport slot 133). The substrate lifter 207 raises the semiconductorsubstrate 311 from the substrate carrier 135 located on the rotary arm201. If not already in place, one of the substrate carriers on thesubstrate traverser mechanism 300, for example, one of the right-mountedsubstrate carriers 305, is traversed to a position behind (i.e., at ornear an extreme position of the traverser end opposite the substratetransport slot 133) the substrate lifter 207. The substrate lifter 207then raises the semiconductor substrate 311 high enough to clear anuppermost carrier surface of the right-mounted substrate carrier 305.The carrier then moves laterally to receive (i.e., to center the carrierunder the substrate-laden lifter) the semiconductor substrate 311 andthe substrate lifter 207 lowers, thus placing the substrate onto theright-mounted substrate carrier 305. The substrate lifter 207 continuesto lower below a plane formed by a lowermost portion of the substratecarrier 135. At this point in time, the rotary arm 201, previouslystopped, may be moved to another position. Once the semiconductorsubstrate 311 is mounted onto the right-mounted substrate carrier 305,the substrate may be linearly transported to the substrate transportslot 133 and transferred back into a slot in the FOUP 113 (see FIG. 1A)by the robot (not shown).

Substantially concurrent with the substrate removal process justdescribed, an unprocessed substrate may be removed, by the robot, fromthe FOUP 113 and placed on, for example, one of the left-mountedsubstrate carriers 307. (Recall, with reference again to FIG. 3, thatthe left-mounted substrate carriers 307 may be considered asdirty-substrate carriers and the right-mounted substrate carriers 305may be considered as clean-substrate carriers). Using one of thesubstrate lifters 207, the unprocessed substrate may be placed on asubstrate carrier of one of the rotary arms 201 that is now stopped. Forexample, the unprocessed substrate may be placed on the same substratecarrier 135 from which the processed substrate, described above, wasjust removed. (Recall, with continued reference to FIG. 3, that each ofthe substrate carriers on the substrate traverser mechanism 300 is movedlaterally at a different elevational height than one another thusavoiding interference between the processed substrate being removed fromthe process chamber 131 and the unprocessed substrate coming into theprocess chamber 131.) Alternatively, the unprocessed substrate may beplaced on a substrate carrier on the opposite end of the rotary arm 201from which the processed wafer was removed. In yet another alternative,the unprocessed substrate may be placed on a substrate carrier on eitherend of any of the rotary arms 201. As a skilled artisan will recognize,additional rotary arms, substrate lifters, and linear substrate carriersmay be added further to enhance substrate throughput.

Further, the described design of the clock-arm substrate carriermechanism 200 and the substrate traverser mechanism 300 allows for eachhand-off of a substrate to be a single axis movement. For example, ahand-off requires two components, a first mechanism to transfer thesubstrate and a second mechanism to receive the substrate. However, asdescribed herein, one of the two mechanisms is not moving (i.e., it isstationary) thus increasing reliability of substrate transfer operationswith substantially reduced communications issues between the twomechanisms (e.g., less stringent timing issues since one mechanism isnot moving). Thus, the robot always has a relatively fixed location withwhich to move a substrate. The fixed location is coupled with a generoustime interval (due to the rotary arms 201 of the clock-arm substratecarrier mechanism 200 being independent from one another). Consequently,a high throughput of over 500 substrates per hour can readily beachieved. Additionally, except for the robot, all movements discussedherein are single axis allowing the clock-arm substrate carriermechanism 200 and the substrate traverser mechanism 300 to be producedrelatively inexpensively.

Notice that the c-shaped structure of the right-mounted substratecarriers 305 and the left-mounted substrate carriers 307 allows eitherof the substrate lifters 207 to be raised and lowered withoutinterference from the substrate carriers. As the substrate lifter 207 israised vertically, fingers of the substrate lifter 207 traverse slots inthe substrate carrier 135. As the substrate lifter 207 continues to beraised, the left-mounted substrate carrier 307 can be moved laterallyuntil it is concentric (i.e., centered with) around the fingers of thesubstrate lifter 207 and, consequently, the semiconductor substrate 311.The substrate lifter 207 then lowers and the semiconductor substrate 311is then captured and held by the left-mounted substrate carrier 307.Although the c-shaped structure is not required for aspects of theinventive subject matter described herein to function, a skilled artisanwill recognize some operational advantages of the c-shaped carrier.Additionally, the skilled artisan will appreciate that, since all of therotary arms 201 can be moved independently of one another, when one ofthe arms stops to be either loaded or unloaded, the other arms maycontinue to move, thereby greatly increasing efficiency and throughputof the overall system.

Referring now to FIG. 5A, a perspective view of a lower chamber portion500 of the process chamber 131 (see FIG. 1B) shows exemplary processchamber exhaust and drain locations used with the exemplary clock-armsubstrate carrier mechanism and substrate traverser mechanism of FIG. 4.Although not actually a part of the exhaust or drain system, the lowerchamber portion 500 is shown to include a pair of openings 501 for thesubstrate lifters 207 (see FIG. 2). Since the pair of openings 501 isnot part of the exhaust or drain system, they are primarily shown forcompleteness of FIG. 5A although an airflow of, for example, about 50cfm (approximately 1.4 m³ per minute) may be drawn through each of thepair of openings 501 to further reduce potential contamination on thesubstrates.

The lower chamber portion 500 is also shown to include a number of outertraverser exhaust ports 503A, 503B, a number of process exhaust ports505A, 505B, a number of inner traverser exhaust ports 507A, 507B and apair of process drain ports 509. The various exhaust ports and drainports are arranged to allow airflow from the FFU 137 (see FIG. 1B) toreduce particulate counts within the process chamber 131 as well asprovide chemical containment. Additional details are provided withreference to FIGS. 7A-7G, below, regarding analysis of the airflow andpressure gradients within the process chamber 131.

FIG. 5B shows a perspective view of an exemplary process chamber exhaustand drain system 550 arranged to mechanically couple below the lowerchamber portion 500 of FIG. 5A. FIG. 5B thus provides a skilled artisanwith a better understanding of how various ones of the exhaust ports anddrain ports of FIG. 5A are interconnected in relationship with theprocess module 130 of FIG. 1B. The process chamber exhaust and drainsystem 550 is also shown to include an inlet process-drain manifold 551,a p-trap 553, and a secondary containment tray 555. The inletprocess-drain manifold 551 couples each of the process drain portstogether below the cross-tube assembly 145. The p-trap 553 provides asubstantially gas-tight seal formed by standing liquid within alowermost portion of the p-trap 553. The standing liquid prevents anygases from a connection to the fabrication facility from back flowinginto the process chamber 131 and thus reduces any chemical or othercontamination from a back-flowed gas. The secondary containment tray 555catches liquids that might otherwise leak or drip from the processmodule 130. In an exemplary embodiment, polyvinylidene difluoride (PVDF)materials can be utilized for the chemical drain lines while chlorinatedpolyvinyl chloride (CPVC) materials can be utilized for the variousairflow lines. A skilled artisan will recognize that other materials,known independently in the art, may be employed as well.

In a specific exemplary embodiment, about 120 cfm (approximately 3.4 m³per minute) of volumetric airflow is drawn from each of the chemicalzones from the process chambers 131 plus an additional 160 cfm(approximately 4.5 m³ per minute) from non-chemical zones of both of theprocess chambers 131 (combined) for a total of about 400 cfm(approximately 11 m³ per minute) from the chambers. In addition toreducing particulate contamination on the substrates within the processchambers 131, the airflow further helps reduce chemical overflow fromone chamber to another and also thus reduces the amount of chemicalvapor that might otherwise escape into the fabrication facility. In thisspecific exemplary embodiment, the total airflow can at least partiallybe broken down as follows. Each of the outer traverser exhaust ports503A draw about 24 cfm (approximately 0.68 m³ per minute) and the outertraverser exhaust ports 503B each draw a 26 cfm (approximately 0.74 m³per minute). Each of the inner traverser exhaust ports 507A draw about12.5 cfm (approximately 0.35 m³ per minute) and the inner traverserexhaust ports 507B each draw about 25 cfm (approximately 0.71 m³ perminute). The process exhaust ports 505A each draw about 48 cfm(approximately 1.4 m³ per minute) and the process exhaust ports 505Beach draw about 52 cfm (approximately 1.5 m³ per minute).

A negative gauge pressure of about 0.5 inches H₂O (approximately 0.9torr) exists near each of the process exhaust ports 505A in the firstchamber exhaust pipe 141 and the second chamber exhaust pipe 143 with aslightly more negative gauge pressure of about 0.6 inches H₂O(approximately 1.1 torr) that exists in exhaust pipes near each of theprocess exhaust ports 505B. An exhaust pressure entering the cross-tubeassembly 145 from the first chamber exhaust pipe 141 is about 0.8 inchesH₂O (approximately 1.5 torr) with a slightly more negative pressure ofabout 1.2 inches H₂O (approximately 2.2 torr) entering the cross-tubeassembly 145 from the second chamber exhaust pipe 143. The process drainports 509 each draw about 6 cfm (approximately 0.17 m³ per minute). Thenegative exhaust pressure at a connection of the chamber exhaust stack147 to a facility interface is about 1.7 inches H₂O (approximately 3.2torr) at about 400 cfm (approximately 11 m³ per minute) of volumetricdraw. Although not shown explicitly, a pressure sensor may be utilizedwithin the chamber exhaust stack 147 to verify chamber airflow. Thepressure sensor can be hard-wired to the processing tool 100 at, forexample, the first operator control interface 115A (see FIG. 1 a) toprevent either system start-up or continued operation should thenegative exhaust pressure fall below a predefined level.

Referring now concurrently to FIG. 1B and FIG. 6, an exemplary airhandling schematic shows volumetric air flow rates into and out from theEFEM 110 and the process module 130 of FIG. 1A. A skilled artisan willrecognize that all volumetric flow rates are approximate only and aregiven as an aid to understanding an overall design of the system. Otherflow rates can be employed. In this exemplary embodiment, a volumetricflow rate of 910 cfm (approximately 25.8 m³ per minute) is generated byone or more fans 601 into a HEPA filter 603 (both of which are withinthe FFU 137). From the original 910 cfm, roughly 590 cfm (approximately16.7 m³ per minute) flows directly across the traverser volume 607, 176cfm (approximately 4.98 m³ per minute) flows into chamber volumes 609,and 145 cfm (approximately 4.10 m³ per minute) of clean excess airflowreturns to the facility ambient through a perimeter slit 753 (see FIG.7B, below) under a hood coupled below the FFU 137. In an exemplaryembodiment, the perimeter slit 753 is about 12 mm in height and formedaround the perimeter of the hood. The excess airflow through theperimeter slit 753 has an exit velocity of about 1 m per second andhelps assure that sufficient airflow is available at all times to thetraverser and chamber volumes should the one or more fans 601 have areduced volumetric air output.

With continued reference to FIG. 1B and FIG. 6, an EFEM port 605 addsanother 90 cfm (approximately 2.5 m³ per minute) into the traverservolume 607, thus maintaining a pressure on any semiconductor substrates311 (see FIG. 3) located on the substrate load stations (see FIG. 1A) tobe at a higher pressure than the traverser volume 607 and reducing orpreventing any chemical or particulate contamination from back-flowingfrom the process chambers 131 into the EFEM 110 and, consequently, intothe fabrication facility. The traverser volume 607 is maintained at apositive pressure with reference to the chamber volumes 609. Thepressure is monitored by a traverser pressure gauge 619A. The traverserpressure gauge 619A may be electronically coupled to one of the operatorcontrol interfaces (e.g., the first operator control interface 115A ofFIG. 1A).

Due to the positive pressure within the traverser volume 607, 64 cfm(approximately 1.8 m³ per minute) of air flows from the traverser volume607 into the chamber volumes 609 and 60 cfm (approximately 1.7 m³ perminute) of air flows into the rail slot volume 611 (containing the innertrack section 203 and the outer track section 205, see FIG. 2). The 64cfm volumetric airflow is generally in the same plane as the carriersand is kept at a velocity that prevents much turbulence in the chamber,but is at a greater velocity than the carrier velocity to preventchemical vapor from being dragged out, between about 3 feet per secondand 10 feet per second (approximately 1 m per second and 3 m persecond). Since the inner track section 203 and the outer track section205 mechanically guide the rotary arms 201, some particulatecontamination is generated where the respective surfaces of the slidingmembers meet. Therefore, the 60 cfm of airflow provides airflow to scrubparticles from the rail slot volume 611 into a scrubbed exhaust 617. Thescrubbed exhaust 617 is maintained at a negative pressure with referenceto the remainder of the system at about 1 to 2 inches of H₂O(approximately 1.9 to 3.7 torr). The traverser volume 607 generatesanother 120 cfm from the pair of traverser exhaust fans 411 (see FIG.4). FIG. 6 indicates the 120 cfm (approximately 3.4 m³ per minute) isdissipated to ambient. However, a skilled artisan will recognize thatthe exhaust from the pair of traverser exhaust fans 411 may optionallybe directed to a floor-drain system volume 613. The remaining 436 cfm(approximately 12.3 m³ per minute) generated into the traverser volume607 is directed into the floor-drain system volume 613.

With reference again to the chamber volumes 609, the chamber volumes 609are also monitored by a chamber pressure gauge 619B. The traverserpressure gauge 619A and the chamber pressure gauge 619B assures thatparticulate contamination and chemical contamination are properly sweptfrom the traverser volume 607 and chamber volumes 609, respectively asindicated, above.

Of the 240 cfm (approximately 6.8 m³ per minute) entering the chambervolumes 609, an adjustable portion of the airflow is directed to thechemical head volumes 615 (relating to the chemical release heads ofFIG. 2) and the rail slot volume 611 with an excess flow being directedto the scrubbed exhaust 617. Other than the 145 cfm of clean excessairflow returning to the facility ambient through the perimeter slit753, substantially all other airflow (which is potentially contaminatedby chemicals or particulates) returns through a floor drain system (FDS)613 within the facility or the scrubbed exhaust 617.

Referring now to FIG. 7A and with continuing reference to FIG. 6, anexemplary perspective view 700 (partially cut away) and an exemplaryplan view 730 of solid components of the process chamber 131 of FIG. 1Bis shown. The solid components are used in computational fluid dynamic(CFD) modeling of various airflows and pressure gradient determinationsas described above with reference to FIG. 58 and FIG. 6. The exemplaryperspective view 700 is shown to include a housing area 703 for the FFU137 (see FIG. 1B) including the one or more fans 601 and the HEPA filter603. A hood 701 couples airflow from the housing area 703 to thesubstrate traverser mechanism (not shown explicitly so as to preserveclarity) and into the process chamber 131. A carrier-arm passage slot705 helps preserve a higher pressure in the traverser volume 607relative to the chamber volumes 609 thus aiding in chemical containmentof outer portions of the process chamber 131. The rotary arms 201 ofFIG. 2 move through the carrier-arm passage slot 705 during operation.The exemplary plan view 730 is shown to include chemical areas 731 inwhich the chemical heads of FIG. 2 may be located.

With reference now to FIG. 7B, a perspective view 750 and a sideelevational view 770 (both views on one side of a line of symmetry) showa fluid domain of the process chamber of FIG. 1B used in thecomputational fluid dynamic modeling utilizing the solid components ofFIG. 7A. FIG. 7B provides an overall understanding of the various CFDmodel flow diagrams and pressure diagrams that follow. In general terms,a combination of a primary air inlet 751 from the FFU 137 and asecondary air inlet 757 from the EFEM 110 delivers airflow into theprocess chamber 131 of FIG. 1B. The perimeter slit 753, described abovewith reference to FIG. 6, provides a clean excess airflow 755 back intothe fabrication facility. The upper chemical-release head 211 andprocess exhaust ports 505A, 505B are shown to assist a skilled artisanin understanding relationships between components of the various figuresdescribed herein (e.g., FIGS. 1B-5B). As discussed with reference toFIG. 6, each of the various exhaust airflows described above areeventually substantially routed to an FDS outlet, thus providing for anexhaust airflow outlet 759.

FIG. 7C through FIG. 7H are included as an aid to assist a artisanskilled in CFD modeling techniques to more fully understand andappreciate various aspects of the inventive subject matter describedwith reference to FIG. 5B and FIG. 6, above. For example, FIG. 7C showsa computed particle trace for a perspective view 750, a plan view 790,and a side elevational view 770 (all three views on one side of a lineof symmetry) within the fluid domain of general airflow motion withinthe process chamber of FIG. 1B. A skilled artisan will recognize thatthe computed particle trace confirms the generalized descriptions givenabove with regard to the air handling schematic of FIG. 6.

FIG. 7D shows a computed pressure field for a perspective view 750 and aplan view 790 (both views on one side of a line of symmetry) to verifylocations of relative pressure differences within the process chamber131. The computed pressure field verifies, for example, both particulateand chemical confinement regions. Both chemical vapors and smallerparticulates (e.g., less than 50 μm) are substantially contained inareas having reduced pressure (i.e., a more negative pressure relativeto other surrounding volumes).

FIG. 7E shows a computed velocity flow field for a perspective view (onone side of a line of symmetry) of general air flow motion from the HEPAinlet within the process chamber while FIG. 7F similarly shows generalair flow motion from a hood slit in the chamber inlet to the variousoutlets.

FIG. 7G shows a computed velocity flow field for a side elevational view(on one side of a line of symmetry) of general air flow motion from theHEPA inlet and the perimeter slit 753 (see FIG. 7B) around one of theionizer bars 139 within a portion of the process chamber. Similarly,FIG. 7H shows a computed pressure field for a side elevational view (onone side of a line of symmetry and without the ionizer bars 139) ofpressure gradients from the HEPA inlet and the perimeter slit 753 withinthe process chamber.

A skilled artisan will appreciate that each of the computed flow andpressure fields shown by the flow and pressure diagrams of FIGS. 7Bthrough 7H are to be considered in light of the physical layout of theexemplary process chamber exhaust and drain system of FIG. 5B and theexemplary air handling schematic of FIG. 6 to more fully understand thevarious exemplary embodiments described herein. A skilled artisan willfurther recognize, given the various descriptions provided herein, thatthe exemplary system for airflow management in a process tool can beimplemented on various tools and at multiple points in a process line.The skilled artisan will further recognize that the system can readilybe incorporated into a plurality of both process and metrology tools invarious portions of a typical fabrication facility (e.g., infront-end-of-line, back-end-of-line, and test operations).

Moreover, although an overview of the inventive subject matter has beendescribed with reference to specific exemplary embodiments, variousmodifications and changes may be made to these embodiments withoutdeparting from the broader spirit and scope of aspects of the inventivesubject matter. Such embodiments of the inventive subject matter may bereferred to herein, individually or collectively, by the term“invention” merely for convenience and without intending to voluntarilylimit the scope of this application to any single invention or inventiveconcept if more than one is, in fact, disclosed. The embodimentsillustrated herein are described in sufficient detail to enable thoseskilled in the art to practice the teachings disclosed. Otherembodiments may be used and derived therefrom, such that structural andlogical substitutions and changes may be made without departing from thescope of this disclosure. The Detailed Description, therefore, is not tobe taken in a limiting sense, and a scope of various embodiments isdefined only by the appended claims, along with the full range ofequivalents to which such claims are entitled.

Moreover, plural instances may be provided for structural elements oroperations described herein as a single instance. Other allocations offunctionality are envisioned. The other allocations may fall within ascope of various embodiments of the present inventive subject matter. Ingeneral, structures and functionality presented as separate resources inthe exemplary configurations may be implemented as a combined structureor resource. Similarly, structures and functionality presented as asingle resource may be implemented as separate resources.

Additionally, many industries allied with the semiconductor industrycould make use of the systems and techniques described herein. Forexample, a thin-film head (TFH) process in the data storage industry, anactive matrix liquid crystal display (AMLCD) in the flat panel displayindustry, or the micro-electromechanical (MEM) industry could readilymake use of the systems and techniques described. The term“semiconductor” should thus be recognized as including theaforementioned and related industries. These and other variations,modifications, additions, and improvements fall within a scope of thepresent invention as represented by the appended claims. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

What is claimed is:
 1. A method of providing airflow management in asubstrate production tool, the method comprising: providing a firstmechanism to couple the substrate production tool to a fan filter unit,the fan filter unit providing filtered air to the substrate productiontool; providing a second mechanism to couple the substrate productiontool to a reduced pressure exhaust mechanism, the reduced pressureexhaust mechanism providing an exhaust for excess gas flow within thesubstrate production tool; maintaining a substrate process area of thesubstrate production tool at a lower pressure than a pressure of asubstrate transfer section of the substrate production tool; maintainingthe substrate process area at a higher pressure than a pressure of thereduced pressure exhaust mechanism; and maintaining the substratetransfer section at a higher pressure than the pressure of the reducedpressure exhaust mechanism.
 2. The method of claim 1, further comprisingproviding one or more substrate transfer slots between the substrateprocess area and the substrate transfer section to allow the lowpressure in the substrate process area relative to the substratetransfer section.
 3. The method of claim 1, further comprising arrangingthe substrate transfer section and the substrate process area to belocated substantially horizontal relative to one another to reduceparticle transport between the substrate transfer section and thesubstrate process area.
 4. The method of claim 1, further comprisingproviding a chemical processing section within the substrate processarea.
 5. The method of claim 4, wherein maintaining the low pressure inthe substrate process area relative to the substrate transfer sectionsubstantially contains chemical vapors within the chemical processingsection from reaching the substrate transfer section.